North Korea, which claimed to have successfully tested a nuclear weapon in 2009, has for years worked to improve its long-range ballistic missile capability. Previous missile tests have been launched east, over Japan. But US intelligence suggests the launch announced for mid-April will be aimed south for the first time.

"If the missile test proceeds as North Korea has indicated, our judgment is that it will impact in an area roughly between Australia, Indonesia and the Philippines," Dr Campbell, the assistant secretary of state for East Asia and the Pacific, said yesterday.

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"We have never seen this trajectory before. We have weighed into each of these countries and asked them to make clear that such a test is provocative and this plan should be discontinued."

After the meeting Mr Carr told the Herald: "The North Korean nuclear and long-range missile plans represent a real and credible threat to the security of the region and to Australia."

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The launch would be "in clear violation of UN Security Council resolutions."

Mr Carr said he and Dr Campbell had "shared views on how both the US and Australia could engage our regional partners and allies to encourage North Korea to abandon its plans".

The US President, Barack Obama, will be among some 50 leaders, including Australia's Prime Minister, Julia Gillard, to meet in a summit in the South Korean capital of Seoul on Monday to discuss nuclear disarmament. North Korea's abrupt announcement last week of its missile test is expected to dominate discussion.

The announcement from Pyongyang startled observers because it came less than three weeks after it had sealed a new agreement with the US in return for food aid.

South Korea has called the move a "grave provocation". Its president, Lee Myung-bak, has said he will ask Mr Obama to revise an alliance agreement that limits his country to missiles with a 300-kilometre range.

Japan's Defence Minister, Naoki Tanaka, said yesterday Tokyo was prepared to shoot down the North Korean long-range rocket if it threatened the country.